This invention relates to novel organometallic complexes. Additionally, the complexes have been discovered to be surprisingly active catalysts for the polymerization of olefins.
The polymerization of olefins using a catalyst having a phosphinimine ligand and a cyclopentadienyl ligand is known and is disclosed for example in copending and commonly assigned U.S. patent application Ser. No. 08/959,589 (Stephan et al) (now U.S Pat. No. 5,965,677). These prior catalysts have an xe2x80x9cactivatablexe2x80x9d ligand which is not a cyclopentadienyl ligand. Exemplary activatable ligands include halides, alkyls, amides and phosphides.
We have now surprisingly discovered and reproducibly synthesized a group of novel organometallic complexes of group 4 metals having a phosphinimine ligand and more than one cyclopentadienyl ligand. These novel complexes form unique crystal structures which may be observed by x-ray techniques.
The organometallic complexes of this invention might be regarded as metallocenes because they contain two or more cyclopentadienyl ligands. It is known that metallocenes of group 4 metals are active catalysts for the polymerization of ethylene. However, we have discovered that certain organometallic complexes of this invention are substantially more active for ethylene polymerization than their simple metallocene analogs.
In one embodiment, the invention provides an organometallic complex defined by the formula: 
wherein M is a group 4 metal in oxidation state 4; each Cp is selected from the group consisting of unsubstituted cyclopentadienyl, substituted cyclopentadienyl, unsubstituted indenyl, substituted indenyl, unsubstituted fluorenyl and substituted fluorenyl; each of R1, R2 and R3 is a hydrocarbyl group which is bonded to phosphorus by a carbon-phosphorus single bond;
n is 2 or 3 and n+p=3; and
when p=1, L is a monoanionic ligand.
Preferred metals are titanium, zirconium and hafnium, particularly titanium.
As noted above, the novel complexes of this invention must contain either 2 or 3 cyclopentadienyl ligands. As such, they may be regarded as metallocenes. The term xe2x80x9ccyclopentadienylxe2x80x9d ligand as used herein is meant to convey its broad but conventional meaning and to be inclusive of both substituted and unsubstituted cyclopentadienyl, indenyl and fluorenyl ligands. Examples of suitable substituents include alkyl groups; halide substituents (i.e. substituents which contain Br, Cl, I or F atoms) or heteroatom substituents (i.e. substituents which contain N, S, O or P atoms). For reasons of low cost and ease of organometallic synthesis, the use of unsubstituted cyclopentadienyl and unsubstituted indenyl ligands is preferred.
The hydrocarbyl groups are preferably alkyl group having from 1 to 10 carbon atoms. Tertiary butyl groups are particularly preferred. The hydrocarbyl groups may also contain substituents, especially halide substituents (i.e. containing Br, Cl, I or F atoms) or heteroatom substituents (i.e. substituents which contain N, S, O or P atoms).